This invention relates to the field of the automatic generation of animation and, more particularly,to an apparatus and method for the automatic generation and coloration and/or shading of images.
Animated films are in widespread use for educational and entertainment purposes. Animated films of reasonably high quality have traditionally been very expensive to make. The initial creative work includes generation of a basic story, a sound track, and basic character designs. Typically, a schedule is generated which describes the movements and timings of each scene to be produced, and layout sketches and "key" drawings are made which define the overall design of each scene. It has been generally observed that at this point most of the creative design work has already been done. The so-called "key" drawings or frames are still frames which show extremes of action. In the traditional animation procedure, people known as "in-betweeners" are employed to sketch frames which fill in the action between key frames. After in-betweens are sketched by hand, the hand-drawn pictures are typically transferred onto celluloid-acetate sheets and are then painted in by hand to obtain the desired image coloration. Much labor is involved in obtaining the in-betweens, which typically comprise the majority of frames of the final work product, and in generating the colored "cels". These tasks render the production of animated films are extremely expensive proposition. An advantage of the traditional animation process, however, is that the animator has virtually complete artistic freedom and control over the resulting film; i.e. anything that is drawn can be made to move in a desired fashion and colors can be precisely selected.
A number of approaches have been proposed for employing electronic equipment to assist in the animation process. For example, some early approaches employed electronic graphical inputs, such as data tablet inputs, to allow an animator to freehand draw sketches which were electronically displayed on a cathode ray tube. The displayed figures can be photographed to obtain basic character outlines to work from in generating the animation as described above. More advanced techniques have employed relatively large scale computer systems to assist the animator and minimize labor. For example, one approach has been to design elaborate special purpose computer systems which can perform coordinate transformations that simulate motion of drawn figures. Techniques of this type are disclosed, for example, in the U.S. Pat. Nos. 3,364,382; 3,662,374; 3,689,917; 3,700,792; 3,710,011; 3,723,803 and 3,747,087. It has also been proposed that a relatively large scale digital computer could be employed to aid the animator, e.g., by automatically generating in-between frames by interpolation of lines appearing in successive key frames. A technique of this type is described, for example, in an article entitled "Towards a Computer Animating Production Tool" by N. Burtnyk and M. Wein which appeared in the proceedings of Eurocomp Conference, Brunel--United Kingdom, May 1974. Also of possible interest are the U.S. Pat. Nos. 3,637,997; 3,665,408; 3,835,245 and 3,944,997.
In general, the described techniques, while potentially easing an animator's labors in various ways, do not adequately provide for the animator's needs in the domain of shading and/or coloring of images. Typically, individual frames, whether key frames or in-between frames obtained by interpolation or by coordinate transformation, have their individual areas colored after they are formulated. Substantial effort is needed to effect coloring of the individual areas of each frame, e.g. by selecting the appropriate primary color components for each area to be colored on each frame and superimposing these components. A somewhat different approach is described in an article entitled "Computer Animation--Some New ANTICS", by Alan Kitching, which appeared in British Kinematography Sound and Television, December 1973. In the ANTICS system, closed polygons representing the outline of the area of a given color are input to a system, such as by using a data tablet. The individual colors which comprise a frame are treated separately and drawn on a data tablet, typically working off-line from a pre-drawn sketch. The frames of an action are "built up" using color components with the final frames being obtained as an accumulation of the figure portions of each color. This technique allows a degree of automation of the coloration procedure, but has the drawback that each figure must be drawn using a somewhat redundant compilation of figure portions which are of a common color component. Typically, it is necessary to do this working from sketches which are predrawn off-line and this can be somewhat wasteful of time as well as limiting on color selection while working.
It is an object of the present invention to provide an apparatus and method for the automatic coloration and/or shading of images which overcomes the problems of the prior art as set forth.